Article · The cup
Rooibos Is Caffeine-Free. It Was Never Decaffeinated.
Rooibos is caffeine-free, which is a different claim from "decaffeinated." Here is the botany, and what decaffeination leaves behind in the coffee that needs it.
Contents · 0% read
Rooibos contains no caffeine. That is a different fact from "decaffeinated," which means caffeine was there and was taken out.
The botany
Aspalathus linearis is a legume, family Fabaceae1. A 1989 survey of the genus Aspalathus and its relatives by South African researchers Van Wyk and Verdoorn2 found the alkaloids sparteine, lupanine and nuttalline in several species, rarely in more than trace quantities.
- Aspalathus linearis (SANBI, PlantZAfrica): Fabaceae, needle leaves, caffeine-free
- Alkaloids of the genera Aspalathus, Rafnia and Wiborgia (Fabaceae-Crotalarieae), Van Wyk and Verdoorn, South African Journal of Botany (1989)
Caffeine is built through three methylations7, meaning a small carbon-and-hydrogen group gets bolted onto the molecule in sequence. Each step is done by an enzyme coded for by a gene. Camellia sinensis has those genes. Coffee has its own, independently evolved version of the same genes4. Cacao has a third, separate version again. A 2016 study in the Proceedings of the National Academy of Sciences3 traced this out: caffeine has evolved at least five separate times across plant lineages, tea, coffee, cacao, citrus, and guarana. Each one recruited old enzymes that originally did something else and repurposed them into a caffeine-making toolkit.
- Molecular Cloning and Functional Characterization of Three Distinct N-Methyltransferases Involved in the Caffeine Biosynthetic Pathway in Coffee Plants, Ogawa et al., Plant Physiology (2001)
- The coffee genome provides insight into the convergent evolution of caffeine biosynthesis, Denoeud et al., Science (2014)
- Convergent evolution of caffeine in plants by co-option of exapted ancestral enzymes, Huang et al., PNAS (2016)
Why "caffeine-free" and "decaffeinated" are not the same claim
Decaffeinated coffee started life with caffeine already in the bean, and it was removed afterward by one of a small handful of industrial processes. Decaffeination typically removes around 97 percent of the caffeine6. The remaining few percent is why a cup of decaf coffee still carries something rather than a true zero.
- Decaf coffee (National Coffee Association): the roughly 97 percent caffeine-removal figure and the decaffeination processes
Decaffeination methods mainly use organic solvents, water or supercritical carbon dioxide5.
- Caffeine in coffee: its removal. Why and how?, Ramalakshmi and Raghavan, Critical Reviews in Food Science and Nutrition (1999): decaffeination by organic solvents, water, and supercritical CO2
What that actually means in the cup
An 8-ounce cup of caffeinated coffee carries about 95 milligrams of caffeine. A decaffeinated 8-ounce cup of coffee still carries roughly 2 to 15 milligrams.
Sources
- Aspalathus linearis (SANBI, PlantZAfrica): Fabaceae, needle leaves, caffeine-free ↩
- Alkaloids of the genera Aspalathus, Rafnia and Wiborgia (Fabaceae-Crotalarieae), Van Wyk and Verdoorn, South African Journal of Botany (1989) ↩
- Convergent evolution of caffeine in plants by co-option of exapted ancestral enzymes, Huang et al., PNAS (2016) ↩
- The coffee genome provides insight into the convergent evolution of caffeine biosynthesis, Denoeud et al., Science (2014) ↩
- Caffeine in coffee: its removal. Why and how?, Ramalakshmi and Raghavan, Critical Reviews in Food Science and Nutrition (1999): decaffeination by organic solvents, water, and supercritical CO2 ↩
- Decaf coffee (National Coffee Association): the roughly 97 percent caffeine-removal figure and the decaffeination processes ↩
- Molecular Cloning and Functional Characterization of Three Distinct N-Methyltransferases Involved in the Caffeine Biosynthetic Pathway in Coffee Plants, Ogawa et al., Plant Physiology (2001) ↩